Device for the selective opening of circuit breakers protecting installations



y 1951 F. J. M. THEUNISSEN 2,551,304

DEVICE FOR, THE SELECTIVE OPENING OF CIRCUIT BREAKERS PROTECTING INSTALLATIONS Filed Dec. 3, 1945 Patented May 1, 1951 DEVICE FOR THE SELECTIVE OPENING OF CIRCUIT BREAKERS PROTECTING IN- STALLATION S Francois Jean Marie Theunissen, Brussels, Belgium Application December 3, 1945, Serial No. 632,443 In Belgium January 25, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires January 25, 1964 (Cl. FEM-98) Claims. I

This invention relates to devices for the selective opening of electric circuit-breakers protecting installations.

When in an installation several circuit-breakers or cut-outs are placed in series, one for example serving as general circuit breaker, and the others protecting the several circuits, it often occurs that in case of a heavy overload. or short-circuit on any one of the circuits, not only the cut-out protecting this particular circuit opens, but also the main or general cut-out, thus breaking the current flow in the whole installation.

The present invention has for its object to aiford an arrangement such that undesired overload current flowing in a given circuit, may be broken by that circuit cut-out which controls this circuit, whilst heavy overloads or shortcircuits are cut exclusively and instantaneously by the general circuit breaker, which opens the circuit for a very short time but which is sufficient for the branch cut-out affected by the shortcircuit to be opened. To attain this object following the principles of the invention the general circuit breaker is connected mechanically to the various branch cut-outs in such manner that in the case of a heavy overload or of a shortcircuit in the branch circuit, the branch cut-out corresponding thereto only opens after the opening of the general or main cut-out. According to the invention, furthermore, the general cut-out closes automatically, immediately after the opening of the branch cut-out affected by the shortcircuit, in such manner as to interrupt the current in the installation only for a very short time.

The element which is called the general circuit-breaker may be constituted advantageously by a contact bridge actuated directly by the electromagnet controlling the general circuit.

As the branch cut-outs each controlling circuits will not, in general, have to cut off very irnportant currents, they may be of very simple design and' construction. Furthermore, although the description which follows shows that as all the elements form part of a unit, the complete device may be such as to conform with the re quirements of practice.

By way of example, an embodiment of the in vention is described hereafter with reference to the annexed drawings in which:

Figure 1 shows diagrammatically in perspective the device applied to a single phase, or pol it being understood that it can be applied to each pole individually with single pole apparatus or to several poles by means of multipolar apparatus.

Figure 2 shows diagrammatically by way of example, the manner in which the general circuit-breaker opens the branch cut-out, the cirsuit of which has caused the operation of the general circuit-breaker.

Figures 3 and 4 show diagrammatically how the general circuit-breaker is in mechanical connection with the various branch cut-outs. In Figure 3, it is assumed that the general circuit breaker is closed; and in Figure l it is assumed open, due to a short-circuit which has been produced in the circuit of the branch cut-out, the disconnecting bar 13 being shown on the diagram in full lines, the bars of the other cut-outs being shown dotted at l3.

In Figure l, i and 2 are the principal contacts of the general circuit-breaker through whi h the current passes. a, b are branch cut-outs each protecting an output to a corresponding branch circuit. The device may comprise any number of branch cut-outs or may even only cornprise a single one.

I is the movable contact carried by the arm 3 of the general circuit-breaker. The arm 3 pivots about the fixed axis 3 and terminates in a cam or boss 5 and a nose piece 5.

'l is a toothed catch pivotally connected at 23 to a dashpot 8 the movable part of which is subjected to the action of a spring tending to displace said part to the right hand side in drawing. A spring 2% attached to the dashpot opposes the downward movement of the catch 1. An electromagnet 9 is arranged adjacent arm 3. Its magnetising coil has one end attached to the axis 4 and its other end to the current network. A spring i ii acts upon the arm 3 to close the contact i and 2. A bar ll rotatably mounted on an axis 22 is constantly held against the arm 3 by a spring i2. This bar extends along the several branch cut outs and is provided with bosses of appropriate profile opposite each branch cut-out to cooperate therewith in a manner that be further described hereafter.

Each branch cut-out comprises the following elements. A fixed contact 2! is connected to the supply line controlled by the general circuit breaker i, 2. A movable contact 26 cooperating with the fixed contact 2! and having a tendency to move away from the latter, is mounted on one arm 2'! of an angle lever 2'1, 28 pivotally mounted at a fixed point 29. A latch mechanism formed by a lever Hi pivoting about a fixed point l5 has a hook 311 which is arranged to one end of the lever I4 and normally engages the end of the arm 28 to hold the movable contact 25 against the fixed contact 2|. A connecting rod I3 is pivotally connected at one end to the other end of the latch I4 and an intermediate point 3! to a rod I6 connected to the core I8 of an electromagnet H. A current output terminal 28 is connected to the circuit controlled by the branch cut-out. The other end of the rod I3 is so positioned that when the said rod is displaced by the electromagnet I'I, I8 into the position I3, the said end is brought into a positionlying in the path of movement of the bar I I when thelatter is allowed to become displaced into the position I I, by the spring I2 during the movement of the arm 3 for opening the contact I. A thermal relay I9 is arranged in such a mannerthat its free end is capable of cooperating with the end of the ratchet lever I4 that is remote from the hook 30.

When the branch cut-out is closed, electric current flows from the contact 2 I, 26 through the elements" 27, 29, Ill, I9 to the terminal 20.

The relay I8 acts in the case of a moderate overload by directly urging the lower end of the lever It to the right and permitting the opening of the contact 26, while the electromagnets 9 and I! act in the case of a heavy overload or shortcircuit. In the latter case the operation is as follows:

The electromagnet II, I8 of the branch circuit in which the short circuit has occurred displaces the rod I3 into the position I3 shown in dotted lines in Fig. 2 and in full in Fig. 4. At the same time the electromagnet 9 displaces the arm 3 to open the contact I against the action of the spring I0, thereby engaging its nose piece 6 into one of the teeth of the catch I. The spring I2 urges the bar II into the position II shown in dotted lines in Fig. 2 and in full in Fig. 4, which interferes with the position of the endof the rod I3 in the position I3, thereby urging this rod to the right so as to move the lever I i about its pivot I5 and disengage its hook 3i] from the end of the lever arm 28. The angle lever 28, 29 then effects a pivotal movement to the right about its axis 29, for instance under the action of spring means (not shown), to open the contact 26, this position being shown in dotted lines Fig. 2 and in full in Fig. 4. The current in the short-circuit'ed circuit thus being interrupted, the electromagnets 9 and I1, I8 no longer act upon the arm 3 and the rod I3 respectively. The spring II! then brings the arm 3 back to its initial position, thereby displacing the bar II to the left hand side in its initial position.

This return movement is preferably braked by the action of a dash-post 8 and opposing spring 25, to be sure that the contacts I and 2 can not 'close again before the contact iii, 25 has been opened. While the moving to the left from the position shown in Fig. 4, the cam or boss 5 abuts against the catch 1 and causes the latter to rock downwards about the pivot 23 against the opposing action of the spring 24, so as to disengage the nose piece 6. At this moment, closing of the contacts I and 2 suddenly takes place. Naturally any other means might be used for braking the return movement of the lever 3 and then sud denly liberating the latter after a certain amount of movement.

Since the current no longer passes through the coil II, the elements I8, I6, I3, I l and 36 also return to their initial positions shown in "full in Fig. 2, but the elements 26, 21, and. 28

remain in the position shown in dotted lines, the contact 2 I, 26 being open.

It is thus clearly seen firstly, that the branch cut-out will never break a current other than that which is limited by a thermal or like relay and secondly that the general circuit breaker which will have broken the excess current, will itself take charge of opening the branch cut-out of the circuit in which the heavy overload has been produced and only this cut-out, to the exclusion of the others connected on to the same general circuit-breaker, since only the connecting rod I3 of this branch cut-out will be placed in the path of the bar II or will come into contact with this latter during its operation.

The faculty circuit being eliminated by its branch cut-out, the whole of the installation with the exception of this circuit will again function normally. In order to avoid any interruption of the current in the other circuits, there may be inserted between the contacts I and 2 a resistance R the amount of which must, however, be sufiicient to avoid an excessive current. in the branch cut-outs. In many cases, a dash -pot or retarding device such as 3 may be dispensed with. Actually, the inertia of the parts to'be set in movement in the general circuit-breaker in order to produce the breaking of the current is much greater than that necessary to displace the bar I3 of the branch cut-out, so that this latter will be in a good position to cause the opening of this cutout, immediately after the breaking of the current has been effected by the general circuitbreaker.

As the damping of the contact I has no other object than to assure the opening of the branch cut-out afiected by the short-circuit, before the contacts I and 2 close again, it will be seen that this damping or braking can in general be dispensed with.

Naturally, without departing from the spirit of the invention, the same could be realised in various constructional forms other than that described above by Way of example.

What I claim is:

1. A device, for the selective opening of circuit-breakers each protecting one of a plurality of branch circuits, and comprising a general circuit-breaker, a plurality of branch cut-outs mounted in series with the general circuitbreaker, means for opening the general circuitbreaker responsive to a heavy overload in any one of the branch circuits, individual locking means for retaining each of the branch cut-outs in closed position, a movable'control member, means for actuating the control member responsive to opening of the general circuit breaker, a movable liberatin member for each branch outout operatively connected to the related locking means, and individual m ans magnetically responsive to the current in the related branch circuit for moving the liberating member to operative position upon the occurrence of a heavy overload in the related branch circuit, the operative position of the liberating member being one in which the member is interposed in the path of movement of the control member thereby to establish a temporary mechanical connection therebetween and in cause the liberation of the lockin means of the related branch cut-out in response to movement of the .control member.

2. A device as claimed in claim 1 wherein the movable control member comprises an element extending adjacent each branch cut-out in a position where its path of movement will be ob- If; structed by the liberating member of any branch cut-out when in operative position.

3. A device as claimed in claim 1 wherein the general circuit breaker comprises a fixed contact, a movable contact and a movable arm carrying the movable contact, the device further comprising means for retarding the closing of the general circuit breaker.

FRANCOIS JEAN MARIE THEUNISSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 957,334 Henderson May 10, 1910 961,164 Rothwell June 14, 1910 1,159,936 Harris Nov. 9, 1915 1,717,260 Rankin June 11, 1929 

